Standard
RLL Instructions
5–103
Standard RLL Instructions
Interrupt Instructions
Interrupt Instructions
O
The Interrupt instruction allows a section of
ladder logic to be placed below the main
body of the program and executed only
when needed. High-Speed I/O Modes 10,
20, and 40 can generate an interrupt. With
Mode 40, you may select an external
interrupt (input X0), or a time-based
interrupt (5–999 mS).
INT
1
INT
Typically, interrupts are used in an application when a fast response to an input is
needed or a program section must execute faster than the normal CPU scan. The
interrupt label and all associated logic must be placed after the End statement in the
program. When an interrupt occurs, the CPU will complete execution of the current
instruction it is processing in ladder logic, then execute the interrupt routine. After
interrupt routine execution, the ladder program resumes from the point at which it
was interrupted.
See Chapter 3, the section on Mode 40 (Interrupt) Operation for more details on
interrupt configuration. In the DL05, only one hardware interrupt is available.
Operand Data Type DL05 Range
Constant O 0, 1
An Interrupt Return is normally executed as
the last instruction in the interrupt routine. It
returns the CPU to the point in the main
program from which it was called. The
Interrupt Return is a stand-alone
instruction (no input contact on the rung).
IRT
The Interrupt Return Conditional
instruction is a optional instruction used
with an input contact to implement a
condtional return from the interrupt
routine. The Interrupt Return is required to
terminate the interrupt routine.
IRTC
The Enable Interrupt instruction is placed in
the main ladder program (before the End
instruction), enabling the interrupt. The
interrupt remains enabled until the program
executes a Disable Interrupt instruction.
ENI
Interrupt
(INT)
Interrupt Return
(IRT)
Interrupt Return
Conditional
(IRTC)
Enable Interrupts
(ENI)
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